var verify_costComment_baseMsg = JSON.parse('{"CODE":0, "ACTION":"","LEVEL":"T1", "MSG":"","DATA":"","SCRIPTNAME":"verify_costComment"}');

if (!isNull(cost) && isNull(cost_comment)) {
    verify_costComment_baseMsg.CODE = 2;
    verify_costComment_baseMsg.ACTION = 'error';
    verify_costComment_baseMsg.MSG = '有更新成本 变成本原因不能为空';
}

JSON.stringify(verify_costComment_baseMsg);